I use a heavy grease on mine, like high temp axle grease, you might also want to check your gas plug to make sure its tight, there are many reasons its short stroking, lubrication is one of if not they most common problem. Also op rod may be rubbing the stock somewhere but this is more common with new stocks not older ones. What type of ammo are you using, reloads, M2ball??
Believe NONE of what you hear; HALF of what you see and ALL you believe
Accuracy is king,penatration is queen but why not jack'em in the process if you can.